The present invention relates to a new and distinct tree of the species Liquidambar styraciflua, which is commonly known as the Sweet Gum Tree. We have called this new cultivar by the cultivar name `Grant's Seedless Zn-4` in honor of Elizabeth May Grant's and William Calloway Grant's discovery and subsequent successful work on the asexual reproduction of the tree. It is anticipated that the tree will be sold under the trademark "Grants' Sunrise".
This new Liquidambar styraciflua tree was discovered in 1983 on the lawn surrounding our new home. On Dec. 24, 1983 the day's high temperature was -11 degrees below zero and the low was minus 23 degrees below zero Fahrenheit (USDA Zone 4b) at Glenview Naval air base (about 3 miles from the location of the tree). That spring we found the tree had not been affected by the extreme cold of that winter as there was more than one foot of new growth on its limbs; and we were also told it had not suffered any damage from the minus 26 degrees cold on Jan. 16, 1982. On Jan. 20, 1985, it survived, without damage, die-back or winter kill, a temperature of minus 31 degrees below zero (USDA Zone 3b) at Glenview and an official record low of minus 27 degrees below zero at the U.S. Weather station at O'Hare Airport, 15 miles south of the tree. We realized the tree was distinct from other L. styraciflua varieties as it did not suffer from the extreme cold of those winters, while similarly exposed trees of the same species were severely damaged or killed. On Jan. 18, 1994, this new cultivar and three of its successive generations created through grafting, also went through the extremes of cold of minus 26 degrees at the Glenview Naval Air base and minus 21 degrees below zero Fahrenheit at the U.S. Weather Station at O'Hare Airport. That spring's new growth of the cuttings that had been grafted onto three common Sweet Gum seedlings was 3 to 5 inches, with no signs of damage, die-back or winter kill on their branches (see FIGS. 4 and 7 of the drawing). One of the specimens of this tree was subsequently transplanted to the Lansing, Mich. area and survived the Michigan winter of 1994-95.
As the owner of the property and the tree with my wife, Carol McGregor Grant, we researched the Sweet Gum Tree, and were surprised to see it survive the winter of 1993's weather without damage. Still I was determined to cut it down and replace it with a Maple variety, as I did not want to put up with the one inch fruits typical of our estimated 20 to 25 year old Sweet Gum. Fortunately, my son, Cal and my daughter Elizabeth, convinced us that we should not "kill" the tree. We promised not to cut it down until the tree developed the pods/fruits typical of L. styraciflua and like the fruits on a Sweet Gum tree six houses distant (approximately 550 feet). By 1986, our tree still had not produced any fruits, even though the neighbor's apparently younger Sweet Gum tree, had produced hundreds of seed pods yearly while also suffering winter die-back. So our originally discovered specimen, saved from the chainsaw by my daughter and son, was thriving through the coldest northern Illinois winters, and each spring it would grow eighteen inches without producing any fruits.
By 1992, almost ten years later, we knew we had a new and distinct variety of Sweet gum, as our tree was both fruitless and hardy. Asexual propagation by grafting cuttings onto common Sweet Gum seedlings was done of our direction at the Morton Arboretum. We Planted three of the grafted seedlings on Jul. 15, 1992. on Jan. 18, 1994 the temperature was minus 26 at Glenview, and minus 21 degrees below zero officially at O'Hare (USDA Zone 4b). All three grafted trees survived without damage and their new growth that spring is illustrated by FIGS. 3 and 5. These asexually reproduced grafted seedlings have proven and demonstrated that they have the novel and distinctive characteristics of this new variety and that they are fixed and hold true under asexual propagation from generation to generation. In 1995, Cal and Elizabeth Grant continued the cultivar's development by grafting 5 more seedlings and by 13 rooted cuttings with a 40% and 25% success rate, respectively.
The two `Moraine` Sweet Gum specimens planted a mile from our trees suffered extensive "die-back" from cold winters and, contrary to recent claims, they have produced seeds and fruits for the past two years. The `Goldust` variety is not hardy, and does not have the same burgundy red to golden-yellow Fall colors nor the same canopy density when compared to the tree of this disclosure. The `Rotundiloba` tree has red rounded leaf lobes, and is only hardy to Zone 6. The `Palo Alto`, `Festival`, and `Burgundy` Sweet Gum trees have seeds, and a greater percentage of Red to Yellow fall color. Finally, unlike many other Sweet gum varieties, our tree also has a canopy that is less dense than usual, as evidenced by the healthy and vigorous growth of lawns underneath specimens of our tree.